I just purchased a clean, well maintained 1991 Trooper with the 4-cylinder & 5-speed, 175,000 miles. It idles and cruises fine. When pushed hard or cruising up hill, it surges and misses. I have not checked anything yet, but will do an ignition timing check. The previous owner reported he did change the cap, wires and plugs somewhat recently. It feels like a fuel delivery problem. Is there an adjustment for the injection system, or a way to service it? I do get a noticeable smell of rubber burning when it warms up. Is there a hose that could have dropped down, melted and is now leaking vacuum?

Additionally, the dome light does not work. There is no power at the unit's manual switch, nor is there ground continuity to the door switch. The fuse block indicates the cabin light's power is on the same fuse circuit as the horn and the horn works. Is there a simple connection that may be loose or corroded from moisture? Is there another switch that activates/deactivates it , like the headlight switch on many vehicles?

Well, since I last posted, I started "fixing" it. I got it running better and better until all that was an issue was the cruising surging. And then the idle surging began. I replaced all of the vacuum hoses but the surging remained. I noticed I was using coolant and a pressure test, though holding steady with the motor off, began climbing dangerously once the motor was started. I did a compression test: 145 / 160 / 125 / 120 (+oil: 150 / 165 / 130 / 125); Vacuum: 21" at idle and steady. So with all of the concerns about cracked heads on these motors, I bit the bullet and moved towards rebuilding the motor. Hey, it keeps me off the streets, eh?

I picked-up a rebuilt short block, a new Clearwater head, a Delta 260 cam, a Pacesetter header and a new clutch & flywheel. It runs great now, except for the surging! Well, not NOW, because I fixed it!

The upper butterfly on the intake assembly was sticking slightly. This assembly was referenced in other posts and I finally addressed it. Since the idle would settle down after blipping the throttle, it seemed like more of a mechanical problem. I also replaced the fuel pump after it finally failed in our 90 degree weather this summer. Between freeing the upper butterfly and installing a new fuel pump, the idle is stable and consistent and does not seem to surge at cruising speeds either. YEA!

Notes regarding rebuild:
- The harmonic balance had slipped 12 degrees!
- I replace all of the hoses, I mean ALL of them.
- On the old motor, oil was leaking from the back of the cylinder head and
from the distributor O-ring.
- On the new motor I am running the valves at +.002" for the first 1000
miles, then will set at .006"/.008" as recommended by Delta. I did
install the VW 8mm lash caps as recommended by Jerry Lemond (WHO
IS AWESOME!!!, <jlemond>, though Delta said it is
unnecessary. This does make the geometry at full open look more
normal and under less stress.
- The Clearwater head came with a stock cam. It is a good thing I
replaced it. I had to literally pry out the installed cam because it was
forced into the front slinger slot. I had to open it up several thousands
with my mighty Dremel tool. Had I not done this, I imagine the timing
belt would have shredded in about 100 miles, if it even lasted that long,
wreaking havoc from interference. I also opened the oil drain return
holes since they were pitifully small. The casting was beautiful but their
quality control was certainly lacking on this head.
- I changed the oil at 500 miles. I am running the ZDDP zinc additive and
will continue to do so. I am running Castrol GTX 10w-30 now and will
change at 2500 miles to Mobil 1.

She's a runner now, with plenty of pull even in 5th gear!

Dome light issues? Well I tracked it down to the contact at the switch on the dome light itself. I cleaned the contacts and the small ball and now everything works except the driver's side, which probably needs a new switch at the door. There is no capability to turn on the dome lights with the headlight switch.

I had a leak. A new windshield, re-using the existing rubber seal and cleaning, priming and sealing the rusty metal surround the windshield was only $150.00, at a local glass shop.

So right now I've got $3500.00, total into this ride, but she should be good to go for quite awhile . . . I hope.

Isn't that dome light the pits? A sto-o-o-pid ball bearing for a contact and it's the ground too at all the switches that makes it screw up.

There is no capability to turn on the dome lights with the headlight switch.

THAT IS THE SILLY TRUTH. This can be fixed with a switch on the dashboard. Just make sure it is a grounding switch. These vehicles use RPL for electrical flow!

When I read the header for your post I wondered: "WOT? The engine runs badly and what's the relationship to the dome light not working got to do with it?"

I was getting ready for a good and long dissertation on things electrical and alternator-wise!

That TPS can cause a lot of troubles as that little screw is NOT for adjusting the idle! Snapping the throttle - when it makes it settle down - usually indicates gunk and grime in the throttle body or someone messed with that screw.

When I rebuilt mine, I just set everything at ZERO timing-wise, both cam and crank and then took the Dremel out and re-notched the harmonic. I figured it would be OK for set-up, but I'd not trust it from that point on.

About the sticky cam - I had something along the same way in that the oil pump was incorrectly assembled (not by me!) and the Woodruff key had jammed into the seal OD and that would have been a mess if I didn't spot it. I chewed on the machine shop that made the block for me - the head was a new casting and all, but the block was a reman.

Moral: Don't trust anybody!

What brand of ZDDP additive did you find? The Torco one isn't available in SoCal - not that I can find it! I'm stuck with Castrol "Tection" in 15/30 w/ZDDP as a propitiatory additive in the bottle. But that's going away as the new bottles have a RED cap verses the BLACK capped ones like before and don't have the same labeling on the back about having ANY ZDDP in it! Rats.

Good looking Trooper, and a fine job of cleaning it up under hood. First thought seeing the yellar' engine was Cat (though obviously a different shade of yellow).
Your comment regarding the cost of a new windshield makes me think I need to get off my rear and get mine replaced. I'm told by the previous owner one of my Troopers is on it's 5th windshield!
Currently 4 Isuzu vehicles and each one has a cracked windshield, beginning to think it's oem!
With that rather flat pan, can the 4 cyl. Trooper engines come out without dropping the axle or pulling the tranny? Pulling the V6 engines rather sucks!

Hanging on the hoist, the cast aluminum oil pan is shown without the steel sump portion.
It bolts to the bottom once the motor is in place. If you look closely, you can see the round oil pick-up
protruding below the aluminum casting. I followed Jerry Lemond's directions (he is so generous with his knowledge!)
and I have copied a portion of them here. By doing as he says, I was able to avoid pulling the transmission, etc.
Removing the hood was pretty easy (like he said) and really afforded a lot more working room.

"Raise the engine up enough with an engine lift to remove both engine mount cushions from the engine and the frame.

Now lower the engine back down on the frame and remove the bellhousing bolts across the top of the engine and down both sides, there are about 9 bolts altogether. Make yourself a diagram as to where they go as they are different lengths. (He is SO right about this!)

Now raise the engine back up and remove the dust shield from the front bottom of the transmission bellhousing.

Now remove the lower oil pan, and the cross beam, 4 bolts at each end.

Gently now, start raising the engine with the lift.

As soon as the bellhousing starts to hit the firewall, stick a piece of 2x4 or a long piece of 3/4 inch pipe under the bellhousing. Let it rest on the torsion bars.

Now lift the engine and pull it forward slowly until it starts to separate from the transmission. Go up and forward and up and forward a little at a time so you don't damage the oil pump pickup pipe. As soon as the pickup pipe is clear of the front differential housing, start lifting the engine and pull slowly forward and it should come right out.

For the install just do this in reverse order. This saves a ton of time by not having to remove that tranny, you don't even have to remove the drive shafts!"

Jerry

THANKS, JERRY!

I was unable to prime the engine before install this way, but it saves a lot of work!
He suggested to fill the oil filter with oil. I packed the oil pump with Vaseline, and spun the starter
without the plugs installed for 30 seconds to get a wee bit of pressure.

Aluminum treatment? Lots of paint thinner, elbow grease, brake cleaner and . . . my secret . . .
keep it off your skin (!!!) . . . Permatex Gasket Remover. This stuff REALLY cleans cast aluminum and it's pretty cheap too.
(Then coat it with clear acrylic.) Beware though, this stuff is HOT when you get it on yourself
(hottest stuff I've ever worked with), but awesome for Offenhauser or Edelbrock manifolds,
makes 'em look new again! Works on Isuzu 2.6 manifolds, too! It took the paint off my newly
cleaned/serviced injectors (www.mrinjector.us) so they don't look as good
as they did a few weeks before, but you take the good with the bad, eh?

I really appreciate Rustoleum enamel. I did use Hi-Temp (VHT) for the block, 2 coats (2 cans) of color
over 1 coat of high temp primer, but half of the bolt-on items got the Rustoleum treatment,
2 coats (over 1 coat of primer) and they're fully covered and looking good.
The other half of bolt-ons received primer and 3+ coats of Krylon and were still not totally yellow,
many areas were a greenish yellow in its attempt to cover the primer. I had to go 4 coats with the Krylon
to get the yellow to be uniform. Krylon was a buck a can cheaper - false economy.

Update:
9.28.09
Do you feel lucky?
11.15.09, 179,284 (3500 miles since rebuild)
Runs great! Lots of power! Highly recommend this head/cam/header combo!
Other mods include:
I did have to replace the fuel pump. I cut a hole in the rear deck for the project, and reinforced the opening with an aluminum plate. I also ran an anti-theft on/off switch up to the console.
I added a late-eighties (first generation) Chrysler mini-van roof rack;
second generation Chrysler mini-van seats with 1.5" extra tilt-back (very comfy) (Gotta love those U-Pull-It yards, eh?);
16x8 Weld Racing wheels (Craigslist specials) and 265x70x16 General Grabber A/Ts. (These are well-rated, reasonably priced and really improve handling versus the worn mudder tires.)
I am getting between 17 and 20 MPG.
I like driving this as much as my VX, honest!
Switched to Mobil 1 5w-40 Turbo Diesel motor oil (I run this in my 3.5L Isuzu VX, beginning at 45k, now with 88k miles), added a serving of Militec treatment (also used in the VX)http://www.militec-1.com/automotive1_old5.html and the ZDDP additive.
I figure I've got $4500 into this. I don't know how I could get this much vehicle for this much money anywhere else!

Last edited by RicksVX on Sun Nov 15, 2009 3:46 pm, edited 1 time in total.

12.05.09
180,000, O2 Sensor "ON." I did not have to remove the speedo/gauge cluster, instead I simply reached up under the dash and slid the switch to the other position. When sitting in the driver's seat, it is just forward of the odometer reset button. Presto!
Installed used limited-slip third member (LSD, aka Posi-traction) from later model Trooper, about 4 hours for project. The Isuzu corporate 12-bolt rear axle found in all Troopers from late 1987-1997, Amigos and pickups through 1994, and all Vehicross models will fit, make sure it is a 4.56 ratio. Put in Royal Purple Synthetic 75w-90 lube.

I was just wondering if the Permatex gasket remover needs to be neutralized when using it to clean aluminum? If so, what would neutralize it? Got a transmission case that needs to be cleaned up and am thinking of trying this.

My experience with the Permatex gasket remover was to remove stains and discoloration on the cast aluminum. I only tried it after getting things as clean as I could get with paint thinner, scrub brush, brake cleaner, and a thorough rinsing with the garden hose. After it was dry I applied the aerosol gasket remover. I let it soak for a time (1/2 hour or so) and just hosed it off. (Maybe I hit again with some more brake cleaner, I don't recall.) After it was dry, I applied a couple of coats of clear Krylon Polyurethane.

Again, don't get that stuff on you! It is HOT! It takes off paint too!

Update, March 2010, 183,500.
EXCESSIVE OIL PRESSURE. Yep, driving around I glanced over at the gauge and it was nearly pegged, like 85psi at cruising speeds! And at idle it was almost as high, like 55psi. Searching the forums here, the response for others with a similar occurrence was to verify the reading with a mechanical gauge and check the electric circuitry.

I visited the local u-pull-it yard and got a sender and gauge cluster ($20.00). I replaced the sender and gauge, and still got similar readings.

Recalling that I had just changed the oil, I replaced the fresh WIX filter with another one. No change.

Since it is an electrical component, I checked the system voltage, I was running 13.9 volts, and under load dropping way down to 11 volts (battery voltage), without the alternator creating any kind of a noticeable load on the motor. My alternator was dying. I replaced the alternator and then the gauge actually registered higher, 60psi at idle (system now at 14.3 volts).

Afraid that oil starvation could be the result of the system trying to maintain the high PSI, I stopped driving it for a few days until I could get back to my sleuthing.

After a few beers I recalled that just prior to noticing the high readings, I had cleaned the motor with aerosol foam and brake cleaner. Then I had really soaped it all down to get off the winter grime. CLUE!

Using the spare gauge I now had, I set it on the fender (isolating it with a piece of foam rubber) and ran a jumper to the sender and then one to the battery, and started the motor. NORMAL READING! Yea! I have the Isuzu factory electronics troubleshooting manual. The wiring from the gauge to the sender actually goes through 3 connectors. Perhaps my exuberant cleaning of the engine compartment contaminated one of the connections? So I ran a dedicated wire from the sender to the gauge and grabbed a 12-volt source from my radio power lead, isolated the gauge from the circuit board with my Dremel tool (I love that thing!) and now have the correct readings displayed on my gauge.

Well, I have been driving this rig without major problems since the rebuild. Now I have noise from the 5-speed in neutral. I believe after 200,000 miles the transmission needs to be rebuilt. The mainshaft had lost its hard-facing at the pocket bearing. $1860.00 R&R with new clutch and we're good for another 200k.

Well, the good folks at Tualatin Transmission in Tualatin, Oregon rebuilt my tranny two more times in a successful (finally) attempt to get it to shift correctly. It would not shift first to second smoothly even after 1000 miles. Everything looked good but they finally ordered the factory synchros. Comparing the two sets, the noticed that the off-the-shelf replacement (non-OEM) synchros are just slightly thicker. The factory synchros work perfectly.